Mann Elizabeth R, Li Xuhang
Elizabeth R Mann, Xuhang Li, Division of Gastroenterology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.
World J Gastroenterol. 2014 Aug 7;20(29):9653-64. doi: 10.3748/wjg.v20.i29.9653.
The intestinal immune system maintains a delicate balance between immunogenicity against invading pathogens and tolerance of the commensal microbiota. Inflammatory bowel disease (IBD) involves a breakdown in tolerance towards the microbiota. Dendritic cells (DC), macrophages (MΦ) and B-cells are known as professional antigen-presenting cells (APC) due to their specialization in presenting processed antigen to T-cells, and in turn shaping types of T-cell responses generated. Intestinal DC are migratory cells, unique in their ability to generate primary T-cell responses in mesenteric lymph nodes or Peyer's patches, whilst MΦ and B-cells contribute to polarization and differentiation of secondary T-cell responses in the gut lamina propria. The antigen-sampling function of gut DC and MΦ enables them to sample bacterial antigens from the gut lumen to determine types of T-cell responses generated. The primary function of intestinal B-cells involves their secretion of large amounts of immunoglobulin A, which in turn contributes to epithelial barrier function and limits immune responses towards to microbiota. Here, we review the role of all three types of APC in intestinal immunity, both in the steady state and in inflammation, and how these cells interact with one another, as well as with the intestinal microenvironment, to shape mucosal immune responses. We describe mechanisms of maintaining intestinal immune tolerance in the steady state but also inappropriate responses of APC to components of the gut microbiota that contribute to pathology in IBD.
肠道免疫系统在针对入侵病原体的免疫原性与对共生微生物群的耐受性之间维持着微妙的平衡。炎症性肠病（IBD）涉及对微生物群耐受性的破坏。树突状细胞（DC）、巨噬细胞（MΦ）和B细胞由于专门将加工后的抗原呈递给T细胞，并进而塑造所产生的T细胞反应类型，而被称为专职抗原呈递细胞（APC）。肠道DC是迁移性细胞，其独特之处在于能够在肠系膜淋巴结或派尔集合淋巴结中产生原发性T细胞反应，而MΦ和B细胞则有助于肠道固有层中继发性T细胞反应的极化和分化。肠道DC和MΦ的抗原采样功能使它们能够从肠腔中采样细菌抗原，以确定所产生的T细胞反应类型。肠道B细胞的主要功能涉及其大量分泌免疫球蛋白A，这反过来又有助于上皮屏障功能，并限制对微生物群的免疫反应。在此，我们综述了这三种类型的APC在肠道免疫中的作用，包括在稳态和炎症状态下，以及这些细胞如何相互作用，以及与肠道微环境相互作用，以塑造黏膜免疫反应。我们描述了在稳态下维持肠道免疫耐受的机制，以及APC对肠道微生物群成分的不适当反应，这些反应导致了IBD的病理过程。
